Biology subjects

Woodford, R.

Publications and source records attributed to Woodford, R..

3 recordsLinked to original sources

bioRxiv2023

NDH complex-mediated cyclic electron flow in bundle sheath cells enables C4 photosynthesis

The superior productivity of C4 plants is achieved via a metabolic C4 cycle which acts as a CO2 pump across mesophyll and bundle sheath (BS) cells and requires an additional input of energy in the form of ATP. Chloroplast NADH dehydrogenase-like complex (NDH) increases ATP production in C3 plants by operating cyclic electron flow (CEF) around Photosystem I (PSI), and its importance for C4 photosynthesis has been proposed from evolutionary and reverse genetics studies. We used the gene-edited C4 species Setaria viridis with null ndhO alleles lacking NDH to study a contribution of the complex to the cell-level electron transport. Our results indicate that NDH is the primary PSI electron acceptor mediating the majority of CEF in BS cells whilst the contribution of the complex to CEF in mesophyll cells is minimal. Moreover, the reduced leaf CO2 assimilation rate and growth of plants lacking the complex cannot be rescued by supplying additional CO2, indicating that NDH is essential for generating ATP required for CO2 fixation by the C3 cycle. Hereby we resolve a cell-level mechanism for the contribution of NDH to supporting high CO2 assimilation rates in C4 photosynthesis.

plant biology↗

bioRxiv2022

Faster responses of photosynthesis to light transitions increase biomass and grain yield in transgenic Sorghum bicolor overexpressing Rieske FeS

Sorghum is one of the most important crops providing food and feed in many of the worlds harsher environments. Sorghum utilises the C4 pathway of photosynthesis in which a biochemical carbon concentrating mechanism results in high CO2 assimilation rates. Overexpressing the Rieske subunit of the Cytochrome b6f complex was previously shown to increase the rate of photosynthetic electron transport and stimulate CO2 assimilation in the model C4 plant Setaria viridis. To test whether productivity of C4 crops could be improved by Rieske overexpression, we created transgenic Sorghum bicolor plants with increased Rieske content. The transgenic plants showed no marked changes in abundance of other photosynthetic proteins or chlorophyll content. Increases in yield of Photosystem II and CO2 assimilation rate as well as faster responses of non-photochemical quenching during transient photosynthetic responses were observed as a result of an elevated in vivo Cytochrome b6f activity in plants overexpressing Rieske. The steady-state rates of electron transport and CO2 assimilation did not differ between transgenic and control plants, suggesting that Cytochrome b6f is not the only factor limiting electron transport in sorghum at high light and high CO2. Nevertheless, more agile responses of photosynthesis to light transitions led to increases in biomass and grain yield in plants overexpressing Rieske. Our results indicate that increasing Rieske content could boost productivity of C4 crops by improving the efficiency of light utilisation and conversion to biomass.

plant biology↗

bioRxiv2022

Rieske FeS overexpression in tobacco provides increased abundance and activity of Cytochrome b6f

Photosynthesis is fundamental for plant growth and yield. The Cytochrome b6f complex catalyses a rate-limiting step in thylakoid electron transport and therefore represents an important point of regulation of photosynthesis. Here we show that overexpression of a single core subunit of Cytochrome b6f, the Rieske FeS protein, led to up to a 40% increase in the abundance of the complex in Nicotiana tabacum (tobacco) and was accompanied by an enhanced in vitro Cytochrome f activity, indicating a full functionality of the complex. Analysis of transgenic plants overexpressing Rieske FeS by the light-induced fluorescence transients technique revealed a more oxidised primary quinone acceptor of Photosystem II (QA) and plastoquinone pool and a faster electron transport from the plastoquinone pool to Photosystem I upon changes in irradiance, compared to control plants. A faster establishing of qE, the energy-dependent component of non-photochemical quenching, in transgenic plants suggested a more rapid build-up of the transmembrane proton gradient, also supporting the increased in vivo Cytochrome b6f activity. However, there was no consistent increase in steady-state rates of electron transport or CO2 assimilation in plants overexpressing Rieske FeS grown in either laboratory conditions or in field trials, suggesting that the in vivo activity of the complex was only transiently increased upon changes in irradiance. Our results show that overexpression of Rieske FeS in tobacco enhances abundance of functional Cytochrome b6f and electron transport capacity and may have a potential to increase plant productivity if combined with other traits. One-sentence summaryIncreased abundance of Cytochrome b6f complex leads to transient increases in photosynthetic electron transport rate in tobacco.

plant biology↗